Brake booster

Abstract

A brake booster includes a casing divided into a constant pressure chamber and a variable pressure chamber by a diaphragm, a power piston attached to the diaphragm, a disc-shaped stem coupled to the center of the power piston and having a through-hole, a plunger interposed between the stem and an input shaft to press/release the stem during reciprocation of the input shaft, and an air intake valve having a vacuum passage interconnecting the constant and variable pressure chambers. The air intake valve is inserted into the diaphragm and the power piston for close contact with the through-hole of the casing, and regulates air flowing from an atmosphere into the variable pressure chamber and from the variable pressure chamber into the constant pressure chamber during the reciprocation of the input shaft.

1. A brake booster comprising:
 a casing divided into a constant pressure chamber and a variable pressure chamber by a diaphragm, the casing having a through-hole in one side thereof; 
 a power piston attached to the diaphragm; 
 a disc-shaped stem coupled to a center of the power piston and having a through-hole; 
 a plunger interposed between the stem and an input shaft connected to a brake pedal, the plunger pressing or releasing the stem by means of reciprocation of the input shaft; and 
 an air intake valve having a vacuum passage through which the constant pressure chamber communicates with the variable pressure chamber, wherein the air intake valve is inserted into the diaphragm and the power piston so as to be in close contact with the casing through-hole, and wherein the air intake valve regulates air flowing from an atmosphere into the variable pressure chamber and air flowing from the variable pressure chamber into the constant pressure chamber by reciprocation of the input shaft. 
 
     
     
       2. The brake booster according to  claim 1 , wherein:
 the air intake valve includes a hollow cylinder and a body extending through and slidably coupled with the cylinder; and 
 the body includes a leading end having a cross-sectional profile corresponding to a cross-sectional profile of the casing through-hole and coming into close contact with an inner surface of the through-hole of the casing, and a trailing end preventing separation of the cylinder. 
 
     
     
       3. The brake booster according to  claim 1 , wherein the air intake valve is configured in such a manner that:
 when the stem is released from the input shaft, a leading end of the air intake valve comes into close contact with the casing through-hole to prevent external air from flowing into the variable pressure chamber and opens the vacuum passage; and 
 when the stem is pressed by the input shaft, the vacuum passage is closed by movement of the cylinder and the leading end of the air intake valve away from the casing through-hole to allow the external air to flow into the variable pressure chamber. 
 
     
     
       4. The brake booster according to  claim 3 , wherein the cylinder has a shape of a circular column. 
     
     
       5. The brake booster according to  claim 4 , wherein the cylinder is screwed to the diaphragm and the power piston. 
     
     
       6. The brake booster according to  claim 3 , wherein the trailing end of the air intake valve has a tapered cross-sectional profile. 
     
     
       7. The brake booster according to  claim 3 , wherein the leading end of the air intake valve has a magnet attached to an outer surface thereof. 
     
     
       8. A brake booster comprising:
 a diaphragm having a first through-hole; 
 a casing having a second through-hole and a third through-hole and divided into a constant pressure chamber and a variable pressure chamber by the diaphragm, wherein the variable pressure chamber is configured to communicate with atmosphere through the second through-hole; 
 a power piston attached to the diaphragm and having a fourth through-hole; 
 a stem coupled to a center of the power piston and a portion of the diaphragm and elastically supported by a first elastic member installed in the constant pressure chamber toward an input shaft; 
 a plunger, one end of which is sealably and slidably coupled through the third through-hole of the casing to the input shaft connected to a brake pedal and the other end of which is slidably coupled to the stem, the plunger pressing or releasing the stem by the input shaft; and 
 an air intake valve inserted into the first through-hole of the diaphragm and the fourth through-hole of the power piston and forming a vacuum passage between the constant pressure chamber and the variable pressure chamber to communicate therebetween with closing or opening the second through-hole to selectively regulate air flowing from the atmosphere into the variable pressure chamber and air flowing from the variable pressure chamber into the constant pressure chamber by the input shaft. 
 
     
     
       9. The brake booster according to  claim 8 , wherein the first elastic member is a compression spring. 
     
     
       10. The brake booster according to  claim 8 , wherein a second elastic member is displaced between the stem and a portion of the plunger in the variable pressure chamber. 
     
     
       11. The brake booster according to  claim 10 , wherein the second elastic member is a compression spring. 
     
     
       12. The brake booster according to  claim 8 , wherein the air intake valve comprises:
 a hollow cylinder to form the vacuum passage therethrough; 
 a body slidably coupled within the cylinder and extending outward the hollow cylinder; 
 a third elastic member biasing the body toward the second through-hole; 
 a trailing end formed at rear end of the body; 
 a leading edge formed at front end of the body; and 
 a holding member formed on the leading edge and opening or closing the vacuum passage between the constant pressure chamber and the variable pressure chamber by selectively blocking the second through-hole of the variable pressure chamber. 
 
     
     
       13. The brake booster according to  claim 12 , wherein a maximum elastic force of the third elastic member is smaller than holding force of the holding member. 
     
     
       14. The brake booster according to  claim 12 , wherein the trailing end has a tapered side cross-sectional shape. 
     
     
       15. The brake booster according to  claim 12 , wherein the trailing end has a step side cross-sectional shape. 
     
     
       16. The brake booster according to  claim 12 , wherein the leading end includes a side cross-sectional shape corresponding to a side cross-sectional shape of the second through-hole of the casing and selectively coming into contact with an inner surface of the second through-hole of the casing. 
     
     
       17. The brake booster according to  claim 12 , wherein the trailing end have a larger diameter than diameter of inner circumference of the hollow cylinder to prevent separation of the body from the hollow cylinder. 
     
     
       18. The brake booster according to  claim 12 , wherein the cylinder is configured to be screwed to the first through-hole of the diaphragm and the fourth through-hole of the power piston. 
     
     
       19. The brake booster according to  claim 12 , wherein the air intake valve is configured in such a manner that:
 when the stem is released from the input shaft, the leading end of the air intake valve comes into close contact with the second through-hole of the casing to prevent external air from flowing into the variable pressure chamber, and the vacuum passage is open; and 
 when the stem is pressed by the input shaft, the vacuum passage is closed by movement of the cylinder, and the leading end of the air intake valve is separated from the second through-hole of the casing to allow the external air to flow into the variable pressure chamber. 
 
     
     
       20. A vehicle brake system, the brake system comprising the brake booster defined in  claim 8 .